Resolving Vega and the inclination controversy with CHARA/MIRC

Abstract

Optical and infrared interferometers definitively established that the photometric standard Vega (=α Lyrae) is a rapidly rotating star viewed nearly pole-on. Recent independent spectroscopic analyses could not reconcile the inferred inclination angle with the observed line profiles, preferring a larger inclination. In order to resolve this controversy, we observed Vega using the six-beam Michigan Infrared Combiner on the Center for High Angular Resolution Astronomy Array. With our greater angular resolution and dense (u, v)-coverage, we find that Vega is rotating less rapidly and with a smaller gravity darkening coefficient than previous interferometric results. Our models are compatible with low photospheric macroturbulence and are also consistent with the possible rotational period of ~0.71 days recently reported based on magnetic field observations. Our updated evolutionary analysis explicitly incorporates rapid rotation, finding Vega to have a mass of 2.15+0.10 – 0.15 M ☉ and an age 700–75 + 150 Myr, substantially older than previous estimates with errors dominated by lingering metallicity uncertainties (Z = 0.006+0.003 – 0.002).